1. Field of the Invention
The present invention relates to an optotype presenting apparatus which presents an optotype for a test including an optotype for a visual acuity test and an optotype for a binocular vision test.
2. Description of Related Art
Conventionally, there is known an optotype presenting apparatus of an irradiation type which is arranged to optically make a light bundle of an optotype, the optotype formed by an optotype forming unit, at a given distance for a test with the use of a projection optical system such as a concave mirror and a beam splitter, and direct the light bundle to an examinee's eye (see Japanese Patent Application Unexamined Publication No. Hei07-236612). In addition, there is known an optotype presenting apparatus of a projection type which is arranged to enlarge and project an optotype formed by an optotype forming unit onto a screen which is apart at a given distance for a test (see Japanese Patent Application Unexamined Publication No. 2003-310552). In each of the conventional optotype forming units of these apparatuses, an optotype disk on which a predetermined optotype image is formed is rotated to selectively place the optotype on an optical path, whereby the desired optotype is presented to an examinee.
However, there is a problem that patterns of the optotypes which can be presented by the above-described apparatuses are limited because the optotypes which can be presented by those apparatuses are optotypes formed on the optotype disks only. There is another problem that because patterns of the optotypes differ among regions where the apparatuses are used, it is required to prepare optotype disks of different patterns. In addition, there is another problem that in order to present an optotype for a binocular vision test such as a stereoscopic vision test and a heterophoria test in which a polarizing plate is used, an exacting task of forming optotypes for a right eye and for a left eye of which polarizing axes are perpendicular to each other on an optotype disk plate is required, which is an arduous work, and causes an increase in production cost.